A wide variety of hydrocarbon conversion processes encountered in the petroleum refining industry are catalytic in nature and many of these processes use crystalline aluminosilicate zeolites as catalysts. Illustrative of such processes include, for example, dewaxing, hydrodewaxing, cracking, hydrocracking, alkylation, isomerization, aromatization, disproportionation and the like. Often, the products from such hydrocarbon conversion processes, or portions thereof, are admixed as blending components to form motor fuels such as gasoline.
In these hydrocarbon conversion processes, various kinds of crystalline aluminosilicate zeolites may be used either alone or in combination with one another or with other catalytic materials. Both natural and synthetic crystalline aluminosilicate zeolites have been employed. Included among these are the type X and type Y zeolites, ZSM-5 and ZSM-20 zeolites, mordenite, as well as zeolite beta.
U.S. Pat. No. 3,308,069 and U.S. Pat. No. Re. 28,341, both issued to Wadlinger et al., disclose a method for preparing zeolite beta. The patents disclose that zeolite beta is prepared from reaction mixtures containing tetraethylammonium hydroxide as the alkali and more specifically by heating in aqueous solution a mixture of the oxides or of materials whose chemical compositions can be completely represented as mixtures of the oxides Na.sub.2 O, Al.sub.2 O.sub.3, [(C.sub.2 H.sub.5).sub.4 N].sub.2 O, SiO.sub.2 and H.sub.2 O suitably at a temperature of about 75.degree.-200.degree. C. until crystallization occurs. The product which crystallizes from the hot reaction mixture is separated, suitably by centrifuging or filtration, washed with water and dried. The material so obtained may be calcined by heating in air or an inert atmosphere at a temperature in the approximate range of 400.degree.-1700.degree. F. or higher so long as the temperature is not sufficient to destroy the crystallinity.
U.S. Pat. No. 4,642,226, issued to Calvert et al., relates to a new and improved form of crystalline silicate having the structure of zeolite beta, to a new and useful improvement in synthesizing said crystalline silicate and to use of said crystalline silicate prepared in accordance herewith as a catalyst for organic compound, e.g., hydrocarbon compound, conversion. The patent discloses the use of dibenzyldimethylammonium as a directing agent, i.e., templating agent, instead of tetraethylammonium hydroxide as described above. The patent further discloses that the zeolite beta can be ion-exchanged by conventional techniques with a salt solution. Following contact with the salt solution of the desired replacing cation, the zeolite is then preferably washed with water and dried at a temperature ranging from 65.degree. to about 315.degree. C. and thereafter may be calcined in air or other inert gas at temperatures ranging from about 200.degree. to about 600.degree. C., preferably from about 200.degree. to about 550.degree. C. for periods of time ranging from 1 to 48 hours or more to produce a catalytically active thermal decomposition product thereof. The patent discloses the use of zeolite beta in hydroisomerization of normal paraffins, when provided with a hydrogenation component, e.g., platinum.
U.S. Pat. No. 4,428,819, issued to Shu et al., discloses a process relating to the hydroisomerization of catalytically dewaxed lubricating oils using zeolite beta. The patent discloses that when the zeolites have been prepared in the presence of organic cations they are catalytically inactive, possibly because the intracrystalline free space is occupied by organic cations from the forming solution. It is further disclosed that the zeolites may be activated by heating in an inert atmosphere at 540.degree. C. for one hour, for example, followed by base exchange with ammonium salts followed by calcination at 540.degree. C. in air.
U.S. Pat. No. 4,554,145, issued to Rubin, discloses a method for the preparation of zeolite beta. In similar fashion to above cited U.S. Pat. No. 4,642,226, the patent discloses that the synthesized zeolite beta can be ion-exchanged with a salt and thereafter calcined in air or other inert gas at temperatures ranging from about 200.degree.-550.degree. C. for periods of time ranging from 1 to 48 hours or more to produce a catalytically active thermal decomposition product thereof. The patent discloses the use of zeolite beta in hydroisomerization of normal paraffins, when provided with a hydrogenation component, e.g., platinum.
U.S. Pat. No. 4,612,108, issued to Angevine et al., describes a hydrocracking process for feedstocks containing high boiling, waxy components using a number of sequential beds of hydrocracking catalyst based on zeolite beta. The proportion of zeolite beta in the catalyst increases in sequence so that the final bed has the highest zeolite concentration. The dewaxing activity of the zeolite beta-containing catalyst is stated to be enhanced by the use of sequential beds in this manner. The pour point of the high boiling fraction is reduced, as well as that of the distillate product, permitting part of the high boiling fraction to be included in the distillate product, thereby increasing the useful distillate yield.
U.S. Pat. No. 4,568,655, issued to Oleck et al. discloses a single catalyst system which is capable of demetalizing, hydrotreating and hydrodewaxing petroleum residue in a single stage process. The catalyst system utilized includes one or more metal oxides or sulfides of Group VIA and Group VIII of the periodic table impregnated on a base of refractory oxide material and zeolite beta. The catalyst also has about 75% of its pore volume in pores no greater than 100 .ANG. units in diameter and about 20% of its pore volume in pores greater than about 300 .ANG. units in diameter.
U.S. Pat. No. 4,301,316, issued to Young, relates to a process for the selective alkylation of substituted or unsubstituted benzene compounds with relatively long chain length alkylating agents to produce phenylalkanes having an improved yield of the more external phenyl isomers. The reaction can be carried out in the presence of a crystalline zeolite catalyst such as zeolite beta.
European Patent Application No. 0 186 447, issued to Mobil Oil Corporation, describes heavy hydrocarbon oils of high paraffin content that are catalytically cracked using zeolite beta. The paraffin content of the oil is at least 20 wt. % or higher. The gasoline cracking products have a high octane rating and the higher boiling products a decreased pour point resulting from the dewaxing activity of the zeolite beta.
European Patent Application No. 0 181 096, issued to Mobil Oil Corporation, discloses a hydrocracking catalyst composition which contains zeolite beta having a framework boron content of 0.1-4.0 wt. %, a solid source of alumina, and a hydrogenation component. The catalyst can be used to hydrocrack heavy hydrocarbon feeds at low pressures.
U.S. Pat. No. 4,554,065, issued to Albinson et al., relates to a process for dewaxing a hydrocarbon feedstock with a relatively high pour point and containing paraffins selected from the group of normal paraffins and slightly branched paraffins which comprises subjecting said feedstock to catalytic dewaxing at catalytic dewaxing conditions by passing said feedstock, along with hydrogen, over a dewaxing catalyst comprising zeolite beta having a noble metal hydrogenation/dehydrogenation component to produce a partially dewaxed product and subjecting said partially dewaxed product to catalytic dewaxing at catalytic dewaxing conditions by passing said partially dewaxed product over catalyst comprising zeolite beta having a base metal hydrogenation/dehydrogenation component to recover a substantially dewaxed product as a product of the process.
U.S. Pat. No. 4,647,368, issued to McGuiness et al., describes an upgrading process for paraffinic naphthas which subjects a full range naphtha to hydrocracking over a zeolite beta hydrocracking catalyst to effect a selective partial hydrocracking in which the higher molecular weight n-paraffinic components of the naphtha are hydrocracked preferentially to the lower molecular weight components with concurrent isomerization of n-paraffins to isoparaffins, to form a hydrocracked effluent which comprises isobutane, C.sub.5 -C.sub.7 paraffins and relatively higher boiling naphthenes and paraffins. The hydrocracked effluent is split to remove the isobutane and the C.sub.5 and C.sub.7 paraffins with the balance of the higher boiling components being used as a reformer feed. Removal of the C.sub.5 and C.sub.7 paraffins permits improved reformer operation with the production of a higher octane product. The isomerization of the paraffins which occurs in the hydrocracking step provides a C.sub.5 -C.sub.7 paraffinic fraction which is of relatively higher octane number because of the shift to isoparaffins, permitting this component to be used as a gasoline blending component.
It can be seen from the disclosures of the above cited patents that zeolite beta has been prepared for use as a catalyst in a variety of hydrocarbon conversion processes. Accordingly, methods are sought for enhancing at least one catalytic property of zeolite beta, preferably catalytic activity and selectivity. Such catalysts could be useful in hydrocarbon conversion processes such as described above, as well as many others.